(1) Field of the Invention
The present invention relates to a pulse absorption circuit for absorbing an abnormal pulse generated at a secondary winding when an input current is cut off at a primary winding of an output transformer in a switching power source.
(2) Description of the Prior Art
Conventionally, a pulse absorption circuit is arranged in an output transformer of a switching power source. In typical conventional pulse absorption circuits S shown in FIGS. 1 to 4, each circuit S is connected between a ground side terminal T.sub.1 of a primary winding of a transformer T and a ground terminal E, i.e., between the collector and emitter of a switching transistor Q. In the arrangement shown in FIG. 1, a snubber comprises a series circuit of a capacitor C and a resistor R. In the arrangement shown in FIG. 2, varister B is used to constitute a pulse absorption circuit. In the arrangement shown in FIG. 3, a Zener diode Z is used to absorb a pulse component having a voltage exceeding a predetermined voltage. In the arrangement shown in FIG. 4, a clamp circuit is arranged wherein a diode D is connected in series with a capacitor C, and a common junction therebetween is connected to a ground terminal E through a resistor R.
In these conventional pulse absorption circuits, pulse energy is absorbed by a circuit loss, thereby degrading efficiency of the power source.